Electroluminescent telephone dial



Oct. 13, 1959 1. A. COHEN ELECTROLUMINESCENT TELEPHONEiDIAL v Filed March 25, 1957 ELECTROIJUMINESCENT TELEPHONE DIAL Irwin A. Cohen, Chicago, Ill., assignor to General Telephone Laboratories, Incorporated, Chicago, 11]., a corporation of Delaware Application March 25, 1957, Serial No. 648,144

2 Claims. (Cl. 240-217) This case refers to telephone dials and more particularly to means for illuminating a dial of this type.

An object of this invention is to provide-a simple means for illuminating a dial.

A further object is "to provide a self-contained lamp in the form of a circular sheet of electroluminescent ma terial.

A feature of the invention is the use of a lamp. which provides sufiicient illumination for dialling purposes and yet consumes but a minor amount of power.

A further feature consists of the use of transparent letters and numbers in the opaque dial number plate in combination with the electroluminescent plate directly behind the number plate. The light provided by. the luminescent plate is transmitted through the transparent letters and numbers. Thus adequate illumination is provided for dialling utilizing but a small fraction of the volume of the dial mounting space available.

The dial used in the present invention is of the type shown generally in- U.S. Patent 2,726,292, issued to R. L. Sargisson on December 6,, 1955. This cited patent shows a number plate having separate annular units for the inner and outer number rings. (The outer surface contour of. this number plate is however similar to that of the number plate in the present application.

The present invention shows a single molded unit comprising the entire number plate as shown in U.S'. Patent 2,563,581, issued to H. R. Clarke on August l,v 1951. The Clarke patent has a concavo-convex cross section while the present invention has a number plate convex in cross section. The remainder of the dial and telephone base are generally of the type shown in the cited Sargisson patent.

In the past there have been many inventions for illuminating a telephone dial. Very few of these have proved commercially feasible and those few have had major drawbacks also. Generally it is required that an electric bulb of some type be placed in the telephone base.

A United States Patent 2,968,806 Patented Oct. 13, 1959' Referring to the drawings, Fig. 1 shows a dial finger wheel with the single piece extended number plate as mentioned previously. This figure also shows a cutaway section of the number plate showing a portion of the electroluminescent sheet. Fig. 2 showsa side view of the dial of Fig. '1. Fig. 3 shows an exploded side View of the lower portion of Fig. 2. Fig. 4 shows a front view of the electroluminescent lamp as used. Fig. 5 shows a method of connecting one of the input leads such as shown in Fig. 1. Fig. 6 shows an alternate method of connecting one of the leads as shown in' Fig. 4.

Reviewing the figures in more detail, Fig. 1 shows a translucent plastic rotatable finger wheel 10 of the type used in many dial telephones. Extended number plate 11 is of a translucent plastic material having an opaque paint on its surface. The plate consists of a single molded section 11 having a slight convexity across the normally visible area, and a substantially flat inner surface, The number plate 11 as shown in Fig. 2 consists of the inner ring area behind finger wheel 10, the extended area and a short cylindrical side section. The area under finger wheel 10 has the triangular or deltoid symbols such as 25 of Fig. l which are tobe illuminated. The extended area of the plate has the characteristic numbers and letters as shown in the cited Sargisson patent which also must be illuminated. Triangles such as 25 and letters and number such as 26 are either masked from the painting process which supplies the surface finish for the plate or are etched after the painting process. In this manner the symbols which are required to be visible are translucent While the remainder of the number plate remains opaque. This feature, of course, has been incorporated in all recent internally illuminated telephone dials.

Lamp 12 in-the form of an annular sheet of the electroluminescent material as shown 'in Fig. 4 is then inserted within the number plate casing 11 as shown in Fig. 2. Plate 12 is composed of a number of layers including a steel conducting? layer 14, a phosphorescent layer 15, a

conductingtr' alnsparen't coating 16 and an insulating film a mains gexposed'. Phenol fi-b'reinsulator 13 is used as a Some means of conducting the light about the periphery of the circular number plate must also be provided. The liabilities incurred by this type of illumination include: first, the use of valuable dial space; second, the necessity of heat dissipation and third, providing adequate lighting of the entire dial surface.

'All of these drawbacks are eliminated by the use of a v electroluminescent lamp of the type shown in U.S. Patent 2,566,349, issued to E. L. Mager on September 4, 1951 backingrfoii-zthe steel :plate'surface' of the lamp and of course to insulate the steel sheet from the remainder of the units in the dial housing. This insulator is blanked to conform in surface area with the shape of the lamp.

Fig. 3 shows the method of locking the electroluminescent lamp into place. This figure is an exploded view, therefore proportions and distance are not wholly accurate. The lamp .12 comprising layers 14, 15, 16 and 17 has the rectangular slot cutout 18 shown in Figs. 1 and 4. Number plate 11 has transverse rib 28 which extends into slot 18 and its horizontal length is about equal to that of the slot. Lamp 12 and insulator 13 both have the same slotted shape and are thereby kept from rotating by the rib to slot fit. Dial base 27 has its circular sidewall contacting the insulator 13 in a concentric circle when mounted thereby retaining the lamp 12 tightly against the rear surface of number plate 11. By using this combination of holding the lamp from rotation by the use of rib 28 and pressing the lamp tightly against the plate, a maximum amount of the luminescence emitted bythe lamp placed in this area also.

nected to the lampfon'e in contact with the steel layer 14 and the other lead in contactiwith conductive layer 16. Each of the leads must be insulated from the other conductive layer (to which it is not connected) by insulation sufiicientto withstand. the applied ,voltage of 110 volt,60 cycles, a 1

Fig. 1 shows eyelet type connectors 19 and 20. Connector 20 of Fig. shows the eyelet which connects to the conductive transparent layer 16 and is insulated from the remaining layers. The eyelet is a small dimension brass eyelet of the type commonly employed in electrical assemblies. The eyelet is produced with one flange already formed. The eyeletis placed in the prepared hole with the flanged end down. The upper extremity may then be crimped to form another flange firmly holding the eyelet in place. Insulating layer. 17 is'removed from the area of contact of the eyelet and the eyelet is insulated from the remaining layers. A male type jack is inserted into the eyelet to. form'the connection to one terminal of the power source. The other eyelet 19 forms the contact to the steel layer 14 andisinsulated from the remaining layers in a similar manner.

Shown in Fig. 4 is the clip type connections 21 and 22. Clip-22 and its connections are shown in more detail in Fig. 6. Clip 22 contacts the transparent conductive surface 16 so that the insulating layer 17 is again removed from the contact area. The'clip 22 is insulated from the remaining layers and wire 23 is soldered to the free end to connect to the power sources A similar clip connection 21 is made to the steel layer for connection to the other terminal of the power source.

With the lamp connected as described to a- 110 volt, 60 cycle souce, a greenish light is produced of sufficient intensity to illuminate the numbers when darkness would make the numbers otherwise invisible. The current neces sary to illuminate the dial is approximately one milliampere so that the power consumption of the unit is low. With this low power drain the life of the lamp should be of many years. duration.

What is claimed is:

1. In a telephone dialling device, a rotatable finger wheel, a number plate adjacent said finger wheel, said number plate having a translucent .body with a. plurality of symbols thereon, said symbols within the surface area covered by said finger wheel and a plurality of symbols on said plate beyond the periphery of said finger wheel;

an opaque outer surface coating covering said number "plate, both said pluralities of symbols comprising configured fenestrations in said opaque coating, means for internally illuminating said symbols through said fenestrations, said illuminating means comprising an electroluminescent annular disc having a surface area substantially equal to the symbol covered area of the number plate surface, means for holding said disc stationary in a firstdirection, said holding means comprising an internal transverse rib in said number plate, a cutout in said disc adapted to receive said rib and to cooperatively lock said disc in said first direction, means in said number plate for affixing thereto from the inward side a dial mechanism having a circular base and sidewall, insulating means adjacent said illuminating means, said insulating means having surface contact with said illuminating means and contact with said sidewall whereby the contact of said sidewall with said illuminating means holds said illuminating means in a second direction.

2. In a telephone dialing device, a circular number plate having an opaque outer surface with a plurality of translucent indicia therein, said number plate having a substantially flat annular inner surface, means for illuminating said indicia from within said device comprising a flat annular electroluminescent lamp, a dial mechanism having a circular base and a sidewall, said mechanism adapted to mount coaxially to said plate, and means interposed between said mechanism and said lamp to maintain line contact with the edge of said sidewall and surface contact with said lamp to retain said lamp against the inner surface of said number plate, a rectangular slot in the periphery of said lamp, means extending inwardly from the inner surface of said plate for cooperatively mating with said slot to thereby position said lamp and also restrain said lamp from rotary movement.

References Cited in the file of this patent UNITED STATES PATENTS 1,383,082 Dodds June 28, 1921 1,466,286 Hearn Aug. 28, 1923 1,850,550 Johnson Mar. 22, 1932 1,955,972 Muse Apr. 24, 1934 2,563,581 Clarke Aug. 7, 1951 2,566,349 Mager Sept. 4, 1951 2,644,861 Jouban July 7, 1953 2,726,292 Sargisson Dec, 6, 1955 

